Address A: Riya Kapoor, 7/2, Lake View Road, Kolkata - 700029
Address B: R. Kapoor, 7/2A, Lake View Rd, Kolkata - 700029
What is the most significant difference between the two addresses? ​​

Given: 

Address A: Riya Kapoor, 7/2, Lake View Road, Kolkata - 700029
Address B: R. Kapoor, 7/2A, Lake View Rd, Kolkata - 700029

Solution:

Address A: 7/2

Address B: 7/2A

Everything else (road, city, surname) is essentially the same.
So, Different house number is the most significant difference between the two addresses.

Thus, correct option is (b).